Data storage systems are used in a variety of different applications. Many different types of data storage systems exist, such as solid-state and non-solid state systems. A disc drive is an example of a type of non-solid state storage system. A disc drive includes at least one rotating disc or storage medium for storage of digital information in a plurality of circular, concentric data tracks. The storage medium passes under a respective bearing slider surface. Each slider carries one or more transducers, which writes information to and reads information from the data surfaces of the disc(s). The slider and transducers are often together referred to as a “head.”
A disc drive also includes an actuator assembly that moves the head or heads from an inner diameter to an outer diameter of a storage medium and across data tracks under control of electronic circuitry. The actuator assembly includes a track accessing arm, a suspension for each head and a voice coil motor. In general, each head is supported by a suspension that is in turn attached to the track accessing arm. The voice coil motor rotates the track accessing arm about a pivot shaft to position a head over a desired data track.
Recently, data storage systems, such as disc drives, are being used to a greater extent in hand-held consumer electronics, such as digital music players, cell phones and personal data assistants. Disc drives that are used in hand-held devices have performance reliability concerns. In particular, the durability of data storage systems in hand-held devices is a major concern. For example, a disc drive in a hand-held device can undergo frequent shock events, such as accidental drops. In addition, some hand-held devices themselves are active shock generators. For example, a hand-held phone set on a vibration mode causes momentary shock events during vibration. Even a ring tone on a hand-held phone can provide a source of momentary shock if the volume is set high enough.
Although some preventative measures exist to address momentary shock, such as operational shock sensors, additional measures are desired to address specific issues. However, some of these additional measures can have undesirable effects. For example, often times burst errors cause a disc drive to repeatably reassign data segments to spare data segments. In addition, burst errors cause a data storage system to reassign many consecutive data segments to spare segments. Repeatable reassignment and consecutive reassignment of data segments during various error bursts can vastly limit an amount of capacity that a data storage system can utilize.